1. Fields of the Invention
The present invention relates to an open wrench, and more particularly, to an open wrench having a pawl clamped between two plate-like head piece to rotate the object.
2. Descriptions of Related Art
The conventional open wrench is disclosed in U.S. Publication No. 2013/0239758 and comprises an elongate body and a head is connected to the body. The head has two jaws and a mounting hole is defined between the two jaws. An opening is defined between two distal ends of the two jaws and communicates with the mounting hole. The axis of the mounting hole is perpendicular to the axis of the body. One of the jaws has a curved recess, a curved guide slot and a notch defined in the inside thereof. The curved recess, the curved guide slot and the notch open toward the direction of the axis of the mounting hole. The other jaw has a curved convex contact face protruding from the inside thereof. The curved guide slot has a first curved face defined in the inside thereof. The notch has a first side which has a first end connected with and is tangential to the end of the first curved face. The second end of the first side is bent to be a second side. The head is cut to have the two jaws with the mounting hole, the curved recess, the contact face, the opening, the curved guide slot and the notch by way of laser cutting or linear cutting. An engaging member is movably received in the curved guide slot and movable along the first curved face. The engaging member has at least one protrusion which is parallel with the axis of the mounting hole. The engaging member has two convex engaging portions. A recessed area is defined at the conjunction area between the two engaging portions. A resilient member is received in the curved guide slot and two ends of the resilient member bias the engaging member and the curved guide slot respectively. To covers are respectively welded to be connected with the head to cover up the engaging member. Each cover has a curved slot which shares a common axis with the first curved face. The at least one protrusion extends through the curved slot. The cover is cut to have the curved slot by way of laser cutting or linear cutting when a hexagonal head clamped in the mounting hole. The diameter of the first curved face is equal to or smaller than the shortest distance of two opposite sides of the hexagonal head. The contact face and a flat inside of the opening are in contact with one side of the hexagonal head. The two engaging portions respectively contact another two opposite sides of the hexagonal head. A corner of the hexagonal head is received in the recessed area between the two engaging portions. The longest distance between the curved recess and the contact face are larger than the distance between two diagonal corners of the hexagonal head. The first curved face is located on a circle and a center of the circle is located within the mounting hole. An angle from 35 to 50 degrees is defined between the shortest distance between the center and the axis of the hexagonal head and the side of the hexagonal head.
However, when the resilient member may disengage from the curved guide slot when the open wrench is returned and the engaging member is moved relative to the body of the wrench. Therefore, an extra piece is used to secure the resilient member in the curved guide slot. This makes the structure be more complicated and the manufacturing cost is increased. Besides, the body of the wrench has a certain thickness so that the pressing force is required to be increased, this increases the stress of the products. The covers are adhered to the body and may be peeled off after a period of time of use.
The present invention intends to provide an open wrench to eliminate the shortcomings mentioned above.